<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>预定义常量</title>
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-base.css" />
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-medium.css" />

 </head>
 <body class="docs"><div class="navbar navbar-fixed-top">
  <div class="navbar-inner clearfix">
    <ul class="nav" style="width: 100%">
      <li style="float: left;"><a href="exif.resources.html">« 资源类型</a></li>
      <li style="float: right;"><a href="ref.exif.html">Exif 函数 »</a></li>
    </ul>
  </div>
</div>
<div id="breadcrumbs" class="clearfix">
  <ul class="breadcrumbs-container">
    <li><a href="index.html">PHP Manual</a></li>
    <li><a href="book.exif.html">Exif</a></li>
    <li>预定义常量</li>
  </ul>
</div>
<div id="layout">
  <div id="layout-content"><div id="exif.constants" class="appendix">
 <h1>预定义常量</h1>

 <p class="simpara">下列常量由此扩展定义，且仅在此扩展编译入 PHP 或在运行时动态载入时可用。</p>
 <p class="para">
  <dl>
   
    <dt id="constant.exif-use-mbstring">
     <strong><code>EXIF_USE_MBSTRING</code></strong> 
     (<span class="type">int</span>)
    </dt>

    <dd>

     <span class="simpara">
      如果启用了 <a href="ref.mbstring.html" class="link">mbstring</a>，这个常量的值为 <code class="literal">1</code>，
      否则为 <code class="literal">0</code>。
     </span>
    </dd>

   
  </dl>

 </p>
 <p class="para">
  <span class="function"><a href="function.exif-imagetype.html" class="function">exif_imagetype()</a></span> 列出几个相关的内建变量。
 </p>
</div>
</div></div></body></html>